Electric motors in which the stator bushings are pushed into the interior of a laminated stator core are known. For example, DE 39 05 773 A1 describes an electric external-rotor motor of this type with a specially designed protective-ground conductor connecting part. In this case, a protective-ground conductor is connected to a laminated stator core via a protective-ground conductor connecting part. The connecting part for this purpose has a center section which extends between a metallic bearing supporting tube and an end insulation shaft of an insulating end plate axially in the direction of the laminated stator core. The connecting part has a first end section, which is connected to the protective ground conductor and extends into a connecting area which is formed between a motor flange and the stator end winding and, for electrical connection, has a second end section which is held with a force fit and/or an interlock by contact with the laminated stator core and with the bearing supporting tube. There is therefore also an embodiment of this generic type in the stator of this known electric motor.
The stator which is known from DE 36 29 049 C2 for an external-rotor motor, has a laminated stator core, stator windings and a motor flange which is arranged on one end face, with the laminated stator core having slots for holding wires of the stator windings, as well as a central, axial aperture opening, into which hollow-cylindrical guide attachments of bearing bushings are inserted from both sides in order to hold shaft bearings for a rotor shaft. In this case, an insulating end plate is in each case arranged directly on the two end faces on the laminated stator core and has a hollow-cylindrical end insulation shaft which axially overhangs the laminated stator core on the end winding face and surrounding the bearing bushing. The insulating end plate which is arranged on the end face opposite the motor flange is formed from plastic integrally with the bearing bushing, its guide attachment and the end insulation shaft. Thus, in comparison with the abovementioned document, there is also a plastic bearing seat, which can be plugged onto the laminated stator core, on the side facing the bottom of the rotor.
Furthermore, EP 769 840 B1 discloses an electric motor without a commutator but with a pressed-in bearing supporting tube. The motor comprises a stator which is attached to a stator flange and has stator windings, an external rotor which surrounds the stator on its side facing away from the stator flange, and an electronics module which is arranged between the stator flange and the external rotor, with power semiconductors, being provided on a circuit board, for whose cooling a specially arranged and designed hollow-cylindrical heat sink is provided. In this case, insulating end plates which can be plugged on are provided in order to insulate the stator windings from the laminated stator core. A bearing supporting tube, which can be pushed in with the laminated stator core, is provided as the bearing for the rotor shaft.
DE 27 12 824 C2 describes a known stator for an external-rotor motor, in which the insulating means, the bearing holding part and the end-winding support are in the form of an integral plastic injection-molded part and enclose the laminated stator core.
A similar embodiment is also known from DE 43 22 575 A1, which describes a bearing arrangement for small electric motors. In this document, at least one bearing element which is seated in a holder in a bearing holding part of a stator is provided in order to support a rotor such that it can rotate. The holder for the bearing holding part is formed on the one hand by dimensionally stable sections which position the bearing element by making contact at least three circumferentially distributed points, and on the other hand by at least one section which can be deformed elastically in the radial direction and holds the bearing element by means of force-fitting contact. The bearing holding parts are designed in particular from the aspect of ensuring a correct, optimum bearing seat without any special machining of the bearing holders. However, motors such as these with a plastic bearing seat are subject to the problem that they have a tendency to oscillate, and this can in turn lead to undesirable noise being formed.
The present invention is based on the object of providing a stator of the generic type described above, which can be produced with less manufacturing effort, but at the same time with the aim of reducing the amount of noise developed as well as improving the electrical insulation of the bearing seat. A further aim is to additionally make it possible to produce a grounding connection for the stator in a simple manner.